Gaia on TAP

Python utilities and examples for accessing ESA Gaia data using Table Access Protocol (TAP).

Authors

• Andrew R. Casey (Monash University)

Installation

Install using pip:

pip install gaia-on-tap

Getting Started

The gaia.tap package includes two main functions for accessing Gaia data: query and cone_search. By default, both will return all retrieved sources as an astropy.table.Table object, so you can then write the results to disk or do something useful with them.

Select stars around M67

# Get all sources within 1 degree of M67

import astropy.coordinates as coord
from gaia.tap import cone_search


cluster = coord.SkyCoord.from_name("M67")

cluster_candidates = cone_search(cluster.ra.deg, cluster.dec.deg, 1.0)

Select hypervelocity star candidates in TGAS

This doesn't treat the errors correctly, but it's a useful example to show what you can do:

import gaia.tap

# Identify stars with tangential velocities exceeding 500 km/s, and reasonable parallaxes
hvs_candidates = gaia.tap.query(
    """ SELECT  * 
        FROM    gaiadr1.tgas_source
        WHERE   parallax_error/parallax < 0.2
          AND   (4.74 * SQRT(POWER(pmra, 2) + POWER(pmdec, 2)))/parallax > 500 """)

Authenticate using your ESA/Gaia Archive credentials

If you have an account with the ESA/Gaia archive, you can include your credentials so that you can upload or query private tables. This is done by having a file (e.g., credentials.yaml) like:

username: acasey
password: my-super-awesome-password

And then in the code:

import gaia

# Read in our credentials. You only have to do this once per Python session!
gaia.config.read("credentials.yaml")

# For any further queries use the authenticate flag, and the code will log you in automagically
sources = gaia.tap.query(" ... ", authenticate=True)

Upload a table to your local space on the ESA/Gaia archive

If you want to upload a VOtable and use it for cross-matches through the ESA/Gaia archive:

import gaia

# Read in our credentials. 
gaia.config.read("credentials.yaml")

# Upload our table, which we will ask ESA/Gaia to call 'my_table'
gaia.tap.upload("my_table", "/local/path/to/your/table.votable")

# Now use it!
# (Ensure that you use the authenticate=True flag so that you can access your private tables)
xmatched_sources = tap.query(
    """ SELECT  *
        FROM    gaiadr1.gaia_source as gaia,
                <YOUR_USERNAME>.my_table as my_table
        WHERE   1=CONTAINS(
                    POINT('ICRS', my_table.ra, my_table.dec),
                    CIRCLE('ICRS', gaia.ra, gaia.dec, 1.5/3600)
                )
    """, authenticate=True)

Resources

• ESA Gaia TAP documentation -> Help -> Command-line access

• Gaia ADQL cookbook

• GAVO ADQL cheat sheet

• Jo Bovy's gaia_tools

• TAP ADQL help on Vizier